Method for measuring enthalpy value of stable isotope labeled ammonium nitrate by using differential scanning calorimeter
By using a high-pressure crucible and one-millionth balance for standard sample calibration in differential scanning calorimetry analysis, the problem of low precision in the determination of thermal enthalpy of stable isotope labeled ammonium nitrate is solved, and high-precision measurement with RSD less than 5% is achieved.
Patent Information
- Application Number
- CN202411733901.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-03-04
AI Technical Summary
The existing differential scanning calorimetry analysis technology is difficult to accurately determine the thermal enthalpy value of stable isotope labeled ammonium nitrate, especially because ammonium nitrate decomposes at 210°C, resulting in a corrosive gas, and the decomposition rate is uncontrollable, resulting in a low precision in determining the thermal enthalpy value.
The standard sample calibration was performed using a high-pressure crucible and one-millionth balance, and the thermal enthalpy value of the stable isotope-labeled ammonium nitrate was determined by a differential scanning calorimeter, and a calibration curve was established through the thermal enthalpy value of the known standard sample to improve the measurement precision.
The precision determination of the thermal enthalpy of stable isotope-labeled ammonium nitrate is achieved, with a precision RSD less than 5%, solving the problem of low precision in the prior art determination of thermal enthalpy in the prior art, and the steps are simple and repetitive.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of stable isotope measurement of thermal enthalpy values, and in particular to a method for measuring the thermal enthalpy value of stable isotope-labeled ammonium nitrate by using a differential scanning calorimeter. Background Art
[0002] Differential Scanning Calorimetry (DSC) is a thermal analysis method that measures the relationship between the heat flow power difference input to the sample and the reference under program-controlled temperature conditions and the temperature. The differential scanning calorimetry method places the sample under a certain temperature program (increase / decrease / constant temperature) and observes the change of the heat flow power difference between the sample and the reference with temperature or time, so as to obtain the relevant thermal effect information such as heat absorption, heat release, and specific heat change of the sample during the temperature program, calculate the heat absorption and release (thermal enthalpy) and characteristic temperature (starting point, peak value, end point, etc.) of the thermal effect, and can be used to measure the enthalpy value, melting point, boiling point, glass transition, heat capacity, crystallization temperature, crystallinity, purity, reaction temperature, reaction heat, etc. of solid and liquid materials.
[0003] Differential scanning calorimetry is widely used in the fields of materials science, biology, chemistry and environmental science. In materials science, DSC is used to study the melting, crystallization and vitrification of materials; in biology, DSC is used to study the stability and conformational changes of biomacromolecules; in chemistry, DSC is used to study the thermodynamic properties of chemical reactions; in environmental science, DSC is used to study the degradation process of pollutants. DSC provides information about phase changes, thermal stability, chemical reactions, etc.
[0004] Stable isotope labeled ammonium nitrate, different element labeling types have different uses, such as 15 N labeling is used in the field of environmental science, etc. In order to study deuterium, 15 N or 18 Whether there are differences in the enthalpy, thermodynamics, and stability of ammonium nitrate labeled with different elements, it is necessary to measure the enthalpy of ammonium nitrate labeled with different elements. However, conventional differential scanning calorimetry is mostly used for qualitative analysis when testing thermally stable substances, and there are few studies on the quantitative analysis of enthalpy, with a precision RSD of about 10%. Stable isotope-labeled ammonium nitrate has different enthalpy values after being labeled with different elements, but the difference is about 10%, and the difference in some labeling forms is less than 5%. Ammonium nitrate is a thermally unstable substance, decomposes at 210°C, produces corrosive gas overflow, and the decomposition rate is uncontrollable. Therefore, conventional differential scanning calorimetry test methods are difficult to determine the enthalpy of stable isotope-labeled ammonium nitrate. Summary of the invention
[0005] The purpose of the present invention is to provide a method for measuring the thermal enthalpy value of stable isotope-labeled ammonium nitrate by using a differential scanning calorimeter, which can be used to measure the thermal enthalpy value of stable isotope-labeled ammonium nitrate.
[0006] The objective of the present invention can be achieved by the following technical scheme: a method for measuring the thermal enthalpy value of stable isotope-labeled ammonium nitrate by using a differential scanning calorimeter, wherein the sensitivity of the differential scanning calorimeter is calibrated by using a standard sample, the stable isotope-labeled ammonium nitrate to be measured is filled in a high-pressure crucible, the thermal enthalpy value of the stable isotope-labeled ammonium nitrate is measured by using the differential scanning calorimeter, and the thermal enthalpy value of the stable isotope-labeled ammonium nitrate is corrected by using the calibrated sensitivity.
[0007] Preferably, the standard samples include water, indium, tin, zinc and lead, and the five standard samples are tested separately and independently.
[0008] Further preferably, the sensitivity of the differential scanning calorimeter is calibrated by establishing a curve using the known enthalpy values of five standard samples and the actual tested enthalpy values.
[0009] Preferably, the stable isotope labeled ammonium nitrate includes deuterium labeled ammonium nitrate, 15 N-labeled ammonium nitrate or 18 O marks ammonium nitrate.
[0010] Further preferably, the labeling type of the stable isotope-labeled ammonium nitrate is single-element labeling or multi-element labeling.
[0011] More preferably, the 15 N-labeled ammonium nitrate 15 The N labeling site is one of ammonium nitrogen labeling, nitrate nitrogen labeling, and both ammonium nitrogen and nitrate nitrogen labeling.
[0012] Preferably, the high-pressure crucible is tightened and sealed with a force of 3N, and is opened with a force of 4N. The high-pressure crucible is cleaned with anhydrous ethanol before each use and used after drying.
[0013] Preferably, the high-pressure crucible is made of gold-plated chromium-nickel steel and has a volume of 10 ml to 50 ml.
[0014] Preferably, the weight of the standard sample or stable isotope-labeled ammonium nitrate is 2.4-2.6 mg.
[0015] Preferably, the standard sample is weighed using a micrometer balance and placed in a high pressure crucible, so as to calibrate the sensitivity of the differential scanning calorimeter using the standard sample.
[0016] Preferably, the stable isotope-labeled ammonium nitrate is weighed using a one-millionth balance, and the stable isotope-labeled ammonium nitrate is placed in a high-pressure crucible to determine the thermal enthalpy value.
[0017] Preferably, the temperature rising program of the differential scanning calorimeter is to hold at 25°C for 10 min, increase the temperature to 400°C at 10 K / min, hold for 5 min, and cool down to 25°C at -20 K / min.
[0018] Preferably, the differential scanning calorimeter uses a high-pressure crucible of the same material without a sample as a reference crucible, the furnace atmosphere is nitrogen, and the gas rate is 20 mL / min to 50 mL / min.
[0019] Preferably, the unit of enthalpy value output by the differential scanning calorimeter is J / g, which is converted into J / mol, and J / g multiplied by the actual molecular weight of the stable isotope-labeled ammonium nitrate sample is J / mol.
[0020] Preferably, 3 to 4 groups of each type of stable isotope-labeled ammonium nitrate are tested and the results are averaged.
[0021] Preferably, in each test, the same high-pressure crucible is used to load the stable isotope-labeled ammonium nitrate to be tested.
[0022] In conventional differential scanning calorimetry analysis, when the commonly used atmospheric pressure crucible is selected, the enthalpy value near 290°C is abnormal, the repeatability is extremely poor, and the precision RSD is close to 80%. Moreover, as a disposable consumable, the background enthalpy value and heat transfer coefficient of each crucible are different. The differential scanning calorimeter consumes only a few milligrams of sample, and the weighing error caused by the balance is one hundred thousandth, which will lead to low precision of the enthalpy value and large RSD.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] 1. The method of the present invention has good precision, with RSD less than 5%, and can be used to determine the thermal enthalpy of stable isotope labeled ammonium nitrate;
[0025] 2. The present invention has the advantages of simple steps, good repeatability, and reliable results, and solves the problem that the existing method cannot accurately determine the enthalpy value of the decomposed sample (ammonium nitrate decomposes at 210°C, and the decomposition process affects the determination of the enthalpy value);
[0026] 3. Based on the thermal enthalpy value results of the present invention, the differences in thermodynamic properties between different isotopes can be studied, laying the foundation for the expansion of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 For differential scanning calorimetry testing 15 Comparison of 3 parallel spectra of N-labeled ammonium nitrate. DETAILED DESCRIPTION
[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0029] A method for measuring the thermal enthalpy value of stable isotope-labeled ammonium nitrate by using a differential scanning calorimeter. The detection method comprises the following steps: fixing the heating rate, weighing a standard sample or the stable isotope-labeled ammonium nitrate by using an electronic balance, placing the standard sample or the stable isotope-labeled ammonium nitrate in a crucible, calibrating the sensitivity of the differential scanning calorimeter by using the standard sample, and correcting the thermal enthalpy value of the stable isotope-labeled ammonium nitrate by using the calibrated sensitivity.
[0030] As a preferred embodiment, the stable isotope labeled ammonium nitrate is deuterium or 15 N or 18 O element tag, the tag type is single element tag or multi-element tag, 15 The N labeling site is one of ammonium nitrogen labeling, nitrate nitrogen labeling, and both ammonium nitrogen and nitrate nitrogen labeling.
[0031] As a preferred solution, the electronic balance is a one-millionth balance.
[0032] As a preferred solution, the standard samples are water, indium, tin, zinc and lead, a total of five kinds of standard samples, and the five kinds of standard samples are tested separately and independently.
[0033] As a preferred solution, a curve is established using known enthalpy values of five standard samples and actual test enthalpy values to calibrate the sensitivity of the differential scanning calorimeter.
[0034] As a preferred embodiment, the crucible is a high-pressure crucible.
[0035] As a preferred solution, in order to ensure the consistency of the enthalpy value of the high-pressure crucible, the high-pressure crucible is used repeatedly, 3N force is used to tighten and seal the high-pressure crucible, 4N force is used to open the high-pressure crucible, and it is wiped with anhydrous ethanol before each use and used after drying.
[0036] As a preferred solution, the unit of enthalpy value output by the differential scanning calorimeter is J / g, which needs to be converted into J / mol. J / g multiplied by the actual molecular weight after stable isotope labeling is J / mol.
[0037] The following describes it in detail with reference to specific embodiments.
[0038] In the following examples, the one-millionth electronic balance used was purchased from Mettler-Toledo Shanghai Co., Ltd., model: WXTS3DU; the 27 ml high-pressure crucible was purchased from NETZSCH Scientific Instruments Trading (Shanghai) Co., Ltd.; the differential scanning calorimeter was purchased from NETZSCH Scientific Instruments Trading (Shanghai) Co., Ltd., model: DSC 200F3; water was ultrapure water (18.2 MΩ*cm); indium was a standard substance, number: GBW(E)130182; tin was a standard substance, number: GBW(E)130183; zinc was a standard substance, number: GBW(E)130185; lead was a standard substance, number: GBW(E)130184.
[0039] Example 1
[0040] Instrument accuracy inspection
[0041] The heating program is to maintain 25℃ for 10min, then increase the temperature to 400℃ at 10K / min and maintain for 5min. Use a 1 / 10 ...
[0042] After the high pressure crucible is dried, water, indium, tin, zinc and lead are tested separately and the above steps are repeated.
[0043] The sensitivity of the differential scanning calorimeter was calibrated by establishing a curve using the known enthalpy values of five standard samples and the actual tested enthalpy values. The calibrated sensitivity was used to correct the enthalpy value of the lead standard sample.
[0044] The theoretical enthalpy of the lead standard is -23.02 J / g, the tested value is -22.76 J / g, and the deviation is 1.1%, which is less than 5%, indicating that the test method has good accuracy and can be used to test stable isotope labeled ammonium nitrate.
[0045] Example 2
[0046] 15 N-labeled ammonium nitrate thermal enthalpy test
[0047] The temperature program was to maintain 25°C for 10 min, then increase the temperature to 400°C at 10 K / min and maintain for 5 min. 2.5 mg was weighed using a 1 / 10000 electronic balance. 15 N-labeled ammonium nitrate was placed in a high-pressure crucible, which was sealed with a force of 3 N. The differential scanning calorimeter was used to detect the thermal enthalpy value. After the test, a curve was established using the known thermal enthalpy values of 5 standard samples and the actual test thermal enthalpy values to calibrate the sensitivity of the differential scanning calorimeter. The calibrated sensitivity was used to correct the 15 The thermal enthalpy value of N-labeled ammonium nitrate nitrate. The thermal enthalpy value output by the differential scanning calorimeter is in J / g, which needs to be converted into J / mol. J / g multiplied by the actual molecular weight after stable isotope labeling 81.043 is J / mol.
[0048] based on Figure 1 The enthalpy values output by the differential scanning calorimeter were calculated to be 115405 J / mol for the first group, 118971 J / mol for the second group, and 115729 J / mol for the third group. The average value was 116702 J / mol, and the precision RSD was 1.7%. RSD less than 5% indicated that the precision of the test results was good.
[0049] Example 3
[0050] Thermal Enthalpy Test of Deuterium-labeled Ammonium Nitrate
[0051] The heating program is to maintain 25℃ for 10min, then increase the temperature to 400℃ at 10K / min and maintain for 5min. Use a 1 / 1000000 electronic balance to weigh 2.5mg of deuterium-labeled ammonium nitrate in a high-pressure crucible, tighten and seal the high-pressure crucible with a force of 3N, and use a differential scanning calorimeter to detect the thermal enthalpy value. After the test is completed, use the known thermal enthalpy values of 5 standard samples and the actual test thermal enthalpy values to establish a curve to calibrate the sensitivity of the differential scanning calorimeter. Use the calibrated sensitivity to calibrate the thermal enthalpy value of deuterium-labeled ammonium nitrate. The thermal enthalpy value output by the differential scanning calorimeter is in J / g, which needs to be converted to J / mol. J / g multiplied by the actual molecular weight after stable isotope labeling 84.043 is J / mol.
[0052] The thermal enthalpy value of the first group is 106567 J / mol, the second group is 104970 J / mol, the third group is 101860 J / mol, the average value is 104465 J / mol, and the precision RSD is 2.3%. RSD less than 5% indicates that the precision of the test results is good.
[0053] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.
Claims
1. A method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using a differential scanning calorimeter, characterized in that: The sensitivity of the differential scanning calorimeter was calibrated using a standard sample, the stable isotope-labeled ammonium nitrate to be tested was loaded into a high-pressure crucible, the enthalpy value of the stable isotope-labeled ammonium nitrate was measured using the differential scanning calorimeter, and the calibrated sensitivity was used to correct the enthalpy value of the stable isotope-labeled ammonium nitrate.
2. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: The standard samples include water, indium, tin, zinc and lead, and the five standard samples are tested separately and independently.
3. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 2, characterized in that: The sensitivity of the differential scanning calorimeter was calibrated by establishing a curve using the known enthalpy values of five standard samples and the actual tested enthalpy values.
4. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: The stable isotope labeled ammonium nitrate includes deuterium labeled ammonium nitrate, 15 N-labeled ammonium nitrate or 18 O marks ammonium nitrate, and the marking type is single element marking or multi-element marking.
5. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: Use 3N force to tighten and seal the high-pressure crucible, and use 4N force to open the high-pressure crucible. Wipe it with anhydrous ethanol before each use and use it after drying.
6. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: The high-pressure crucible is made of gold-plated chromium-nickel steel, with a volume of 10 ml to 50 ml, and the weight of the standard sample or stable isotope-labeled ammonium nitrate is 2.4 to 2.6 mg.
7. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: Weigh the standard sample or stable isotope labeled ammonium nitrate using a 1 / 10000 balance and place the standard sample or stable isotope labeled ammonium nitrate into a high pressure crucible.
8. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: The temperature program of the differential scanning calorimeter was to hold at 25°C for 10 min, increase the temperature to 400°C at 10 K / min, hold for 5 min, and then cool down to 25°C at -20 K / min.
9. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: The differential scanning calorimeter uses a high-pressure crucible of the same material but without a sample as a reference crucible, and the furnace atmosphere is nitrogen with a gas rate of 20 mL / min to 50 mL / min.
10. The method for measuring the thermal enthalpy of stable isotope labeled ammonium nitrate using differential scanning calorimetry according to claim 1, characterized in that: The unit of enthalpy value output by the differential scanning calorimeter is J / g, which is converted into J / mol. J / g multiplied by the actual molecular weight of the stable isotope-labeled ammonium nitrate sample is J / mol; 3 to 4 groups of each stable isotope labeled ammonium nitrate were tested, and the results were averaged; In each test, the same high-pressure crucible was used to load the stable isotope-labeled ammonium nitrate to be tested.